Nowadays, synchronous machines are used in a multiplicity of applications. For example, in the case of a gas-turbine power station having a plurality of gas turbines and generators which are connected to the gas turbines and are in the form of synchronous machines, the synchronous machines can be used to start the gas turbines. A starting apparatus which starts the synchronous machines and therefore also the gas turbines can be used for this purpose. FIG. 1 shows one modern known starting apparatus for at least two synchronous machines. In this Figure, the starting apparatus has an exciter unit SES which is provided for each synchronous machine G and is associated with the respective synchronous machine G, with the respective exciter unit SES being connected to the field winding of the associated synchronous machine G and being used to feed the field winding. A superordinate control unit DCS is also provided, with the superordinate control unit DCS being connected via a communication link to each exciter unit SES. Like other communication links which will also be mentioned, the communication link is represented by a dashed line in FIG. 1. Furthermore, at least one stator feed unit SSD and a switching device SSB are provided. A switching device SSB is provided for each stator feed unit SSD and is associated with the respective stator feed unit SSD, in which case the respective switching device SSB can be connected to the associated stator feed unit SSD, the respective switching device SSB can be connected to at least one synchronous machine G, and the switching devices SSB can be connected to one another when there are a plurality of switching devices SSB. The superordinate control unit DCS is connected via a communication link to each switching device SSB. Furthermore, the superordinate control unit DCS is connected via a communication link to each stator feed unit SSD.
When it is now intended to start a synchronous machine G by a known starting apparatus as shown in FIG. 1, the superordinate control unit DCS passes an appropriate signal via the communication link to the exciter unit SES, which then applies an exciter voltage to the field winding of the synchronous machine G that is being started. Furthermore, the superordinate control unit DCS passes an appropriate signal via the communication link to one or more switching devices SSB, in response to which a stator feed unit SSD, which selects the superordinate control unit DCS via the communication link using a signal, is connected to the stator winding of the synchronous machine G due to be started, with the stator feed unit SSD applying a feed voltage to the stator winding and then starting the desired synchronous machine G.
The starting apparatus as described above and as shown in FIG. 1 can be subject to a communication link which exists in each case from the superordinate control unit DCS to each exciter unit SES, to each switching device SSB and to each stator feed unit SSD. The superordinate control unit DCS can be integrated in a central control station, well away from the synchronous machines G, from the exciter units SES, from the switching devices SSB and from the stator feed units SSD. As a result, the communication links can cover large distances, as a result of which the starting apparatus can be complex to implement and to maintain, and the susceptibility to defect can rise. A further factor which can affect the susceptibility to defects of the starting apparatus as described above and shown in FIG. 1 is that the superordinate control unit DCS can include virtually all the control tasks for the starting process, and the superordinate control unit DCS therefore can have to carry out virtually all the central control functions. However, if one or more communication links of the superordinate control unit DCS is interrupted, for example because of a fault, then operation of the starting apparatus can be either completely impossible or no longer worthwhile, with the starting apparatus then no longer being available.